Field of the Invention
The present invention relates to a technique to remove an unnecessary background on a scanned image at the time of copying a document.
Description of the Related Art
In general, in copy processing in an image forming apparatus, such as a Multi Function Peripheral (MFP), in order to reproduce a document to be copied faithfully, various kinds of image processing are performed for an image (scanned image) obtained by reading the document by a scanner. At this time, it is preferable for so-called show-through, which is a phenomenon in which an image on the backside of a document shows through, not to be reproduced faithfully. Further, for example, in the case where a document to be copied is newspaper, it is rather preferable not to faithfully reproduce the color (background color) of the paper itself. As described above, on a scanned image, unnecessary background information (hereafter, called “unnecessary background”) that a user does not intend to print may also be included. As a representative function to remove such an unnecessary background, there is a background removal function. In the general background removal, in the case where the signal value of each color is greater than or equal to a predetermined value, processing to convert the signal value into a value corresponding to white is performed. convert the signal value into a value corresponding to white is performed.
Here, there is such a problem that even a highlight area that should be left originally is removed along with the unnecessary background within the scanned image by the above-described background removal function. For this problem, a method has been proposed, in which a halftone dot portion within a scanned image is determined and the background is removed only in the case where the portion is not a halftone dot and the density is lower than or equal to a fixed density (see Japanese Patent Laid-Open No. 2002-77607).
With the technique disclosed in Japanese Patent Laid-Open No. 2002-77607 described above, the halftone dot portion within the scanned image is not removed. Because of this, for example, in the case where part of a show-through portion is determined to be a halftone dot, there arises such another problem that the show-through portion is left as unevenness.